The Related Theoretical And Experimental Research On Obtaining High-speed Physical Random Numbers Based On Semiconductor Laser Chaotic Entropy Source

With the rapid development and wide application of network technology,human society has entered the information age.Information is both time and wealth.It is an important strategic resource for national development.However,information should be protected,because it could suffer unauthorized access,tamper or breach in the transmission process of communication network.The core technology of information security is cryptography.In the field of cryptography,random numbers are used in encryption technology,digital signature,identify authentication and various security protocols.Therefore,random number is the footstone of cryptography,its quality determines the security of cryptography.According to the generating method of random number,random number generators can be divided into two categories: Pseudo Random Number Generator and Physical Random Number Generator.By using seed sequence and deterministic algorithm,pseudo random number generator can easily generate the random number sequence with a rate of Gbits/s by computer.Because of its low cost,output rate mainly limited by processor speed only,easy to break the speed bottleneck and excellent sequence statistical characteristics,pseudo random number generator is widely used in Monte Carlo simulation,statistical sampling and other scientific calculation fields.Nevertheless,due to the determinacy of these generators,the output random bit sequences from these generators have inevitable periodicity,the available sequence length is limited,and it does not have real randomness in essence.This feature makes the pseudo random number generator have security risks when it is used in the field of secure communication.With the rapid development of quantum computing,cloud computing and other fields,the rapid improvement of computing resources makes the pseudorandom number generator based on computing complexity more and more difficult to meet the needs of information security.In fact,as Schneier,a famous applied cryptographer,said,the best way to collect a large number of random numbers is to select the natural randomness in the real world.Physical random number generator is,generally speaking,based on the random phenomenon in the real world as the entropy resource to generate random number.The random number generated by this generator is non periodic,unpredictable and has real randomness.However,limited by selected physical mechanism,traditional physical random number generator can only generate random number with a typical rate of Mbits/s,which can not meet the rate requirements of the future high-speed secure communication network.Recently,the scheme of random number generator based on semiconductor lasers chaotic entropy source has been widely concerned.The bandwidth of the broadband chaotic laser signal output from the semiconductor device has be as high as several GHz.And the chaotic signal has a wide range of intensity fluctuations,is easy to extract.Therefore it is very suitable for generating high-speed random numbers with a rate of more than Gbits/s,which shows great application potential in the field of high-speed confidential communication.This thesis focuses on the research of obtaining high-speed physical random numbers from semiconductor laser chaotic entropy sources.The main research contents and conclusions are as follows:1.This work proposes a technical scheme for generating multiple channels random numbers based on the chaotic laser output from the mutual coupling distributed feedback semiconductor lasers(DFB-SLs)system.On the one side,the mutual coupling DFB-SLs system is modeled by the Lang-Kobayashi rate equation.The fourth-order Runge-Kutta method is used to solve the rate equation,and the system outputs are in chaotic state by appropriately selecting the coupling strength and the coupling delay time.The time series of the outputs of the mutual coupling DFB-SLs system under different parameters are numerically simulated,and the time delay signature of chaotic output of the two lasers in the system are extracted and quantified using correlation functions and mutual information.Under the condition of fixed coupling delay time,the evolution characteristics of the time delay signature peaks of the autocorrelation function of time series from the two lasers chaotic output under different coupling intensities are analyzed,and the influence of frequency detuning on the time delay signature of the system outputs is also analyzed.On the other side,an experimental system of mutual coupling DFB-SLs is construct based on the above theoretical research.Firstly,two high-quality chaotic entropy source signals with sufficiently suppressed time delay signature are obtained through time delay signature suppression technology,and the entropy source is sampled and quantized by an 8-bit analog-to-digital converter(ADC)in an undersampling manner.Through simple post-processing,two sets of 50 Gbits/s random numbers are obtained,which have been tested by all NIST statistical test.Subsequently,the optical spectra,radio-frequency(RF)spectra,and chaotic bandwidth evolution with the coupling strength of the system outputs were studied experimentally.The evolution trend of the amplitude probability density distribution,autocorrelation curve and time-delay signal peaks of the chaotic entropy source time-domain waveform samples with the change of coupling strength was evaluated.The entropy source is sampled and quantized by oversampling,and a complex post-processing method is used to finally obtain a dual-channel random number which meets stringent quality evaluation standards and has a rate of 0.48 Tbits/s,and a 0.96 Tbits/s random number is obtained by utilizing bitwise interleaving.2.A technique scheme for obtaining multi-channel random numbers based on a master-slave vertical-cavity surface-emitting lasers(VCSELs)chaotic system is proposed.Firstly,we set up the experimental system of a VCSEL under chaotic optical injection.By introducing parallel optical feedback and optimizing the feedback parameters,the two orthogonal polarization modes of the master VCSEL are excited into chaotic state simultaneously.Then,the two paths of chaotic light output from the master VCSEL are injected into the slave VCSEL,so that the two orthogonal polarization modes of the slave VCSEL are also excited into the chaotic state.We analyze the influence of the injection power,the frequency detuning between the central frequency of the two VCSELs on the effective bandwidth,permutation entropy and maximum correlation coefficients of the two polarization chaotic signals output from the slave VCSEL.In the optimal parameter condition,the chaotic signals output from the two-polarization mode of the slave VCSEL are used as entropy sources to generate random numbers.The influences of different post-processing methods on the statistical characteristics and time delay signatures of the output sequences were discussed,and random numbers at dual-channel rate of 160 Gbits/s were finally obtained.In view of the problems exposed in the research process of the above experimental scheme,we propose an improved scheme to obtain multi-channel random numbers by injecting the chaotic light(from master VCSEL based on the fiber Bragg grating(FBG)external cavity)into slave VCSEL.Firstly,based on the spin-flip model of VCSEL,the rate equation of the system is derived.The influence of FBG external cavity feedback intensity,frequency detuning(between FBG and master VCSEL)on the effective bandwidth and time delay signature of the two orthogonal polarization modes output signals from the master VCSEL are studied theoretically.The bandwidth of the slave VCSEL chaotic output based on dual-path polarization-preserved optical injection is also calculated.Based on above theoretical investigations,we construct the corresponding experimental system.The influence of FBG external cavity feedback intensity on the effective bandwidth and time delay signatures of the chaotic outputs from the master VCSEL is studied under the condition of two-mode coexistence.Based on dual-path polarization-preserved optical injection,the time delay signature and effective bandwidth of chaotic entropy sources from the two polarization modes of slave VCSEL are studied.Under the optimal parameters,the two chaotic entropy sources are extracted in parallel and combined with post-processing techniques.Finally,20 sets of random numbers with the rate of 160Gbits/s conforming to the NIST standard are generated.3.A scheme of obtaining high-speed random number is proposed based on the FBG external cavity WRC-FPLD.The time series,optical spectrum and power spectrum of WRC-FPLD output are collected and analyzed by using digital oscilloscope,spectrometer and spectrum analyzer.The dynamic evolution path of WRC-FPLD output is studied experimentally.With the increase of feedback power,the output of WRC-FPLD presents an evolution process from stable state,to single periodic state,then enter chaotic state,and finally return to stable state.Under three different FBG bandwidths,the evolution of the effective bandwidth of chaotic signals(from 35 longitudinal modes in the wavelength range of 20nm)with the feedback power variation is investigated.The analysis shows that 35 longitudinal modes of WRC-FPLD can enter into chaotic state respectively by adjusting the center wavelength of FBG and selecting the feedback power appropriately.With the increase of filter bandwidth,the chaotic bandwidth of longitudinal mode outputs are enhanced.Under the filter bandwidth of 100 GHz,the chaotic effective bandwidth of each longitudinal mode outputs can reach more than 20 GHz with flat spectrum.By selecting the chaotic output with 23.9GHz effective bandwidth as the entropy source,and adopting appropriate post processing,the random number which meets the rigorous quality evaluation standard can be obtained at the rate of 240Gbits/s.